The present invention relates to an array substrate and a liquid crystal display (LCD) comprising the same.
LCDs are a common type of flat panel displays, an example of which is thin film transistor-liquid crystal display (TFT-LCDs). TFT-LCDs generally have a structure as shown in FIG. 1 and comprise a backlight unit (BLU) 10, an optical film 20, and a liquid crystal panel 30 disposed in the order from bottom to top, and the liquid crystal panel 30 is typically formed by attaching a color filter (CF) substrate 31 to an array substrate 32 with a liquid crystal layer (not shown) provided therebetween. The TFT-LCD can further comprise a mold frame disposed at sides of the backlight unit 10, the optical film 20 and the panel 30 for supporting and fixing them, including an outer frame 40 disposed most outside. In general, the backlight unit 10 may include a light guide plate 11, a back light source 12, a back plate 13 and so on. The optical film 20 may comprise, for example, a diffusion film, a prism film, and the like, so as to control light emitted from the light guide plate 11 to the liquid crystal panel 30. The various optical films may be collectively referred to as the optical film 20.
The array substrate 32 of the panel 30 generally includes an array of pixels arranged in a matrix form, as shown in FIG. 2, which is a schematically partial top view of the array substrate 32. Each pixel includes a pixel electrode (ITO) 322 and a gate line 321 and a data line 323 that are disposed at sides of the pixel electrode 322 and perpendicular to each other. The pixel electrode 322 is connected to the gate line 321 and the data line 323 via for example, a thin film transistor (TFT) switch element 325. A light-blocking strip 324 is provided in a gap between the data line 323 and the pixel electrode 322 to block light emitted thereto from the backlight unit 10. FIG. 3 is a cross-sectional view of the array substrate 32 taken along line A-A in FIG. 2 together with the color filter substrate 31 provided above the array substrate 32. The array substrate includes a base substrate 326 with the light-blocking strip 324, the data line 323 and the pixel electrode 322 disposed thereon. An insulating layer may be formed between the data line 323, the light-blocking strip 324 and other elements so as to prevent them from being electrically connected with each other. The liquid crystal layer 33 is injected into the space between the color filter substrate 31 and the array substrate 32. As shown in FIG. 3, a black matrix 311 is disposed at the inner side of the color filter substrate 31 for sheltering functional elements on the array substrate 32 other than the pixel electrode 322, and these functional elements comprise the data line 323, the light-blocking strip 324, and the like.
In operation, light emitted from the backlight unit may pass through the gap between the light-blocking strip 324 and the data line 323, as shown in FIG. 3. Light passing through the gap includes a portion that is illuminated perpendicular to the array substrate 32 and a portion that is illuminated obliquely at an acute angle relative to the array substrate 32. When passing through the base substrate 326 of the array substrate 32 and the liquid crystal layer 33, the obliquely illuminated light may be deflected due to refraction due to the refractive index difference between respective materials. The base substrate 326 is typically formed of glass, of which the refractive index is 1.5, assuming that the refractive index of air is 1. Refractive index of the liquid crystal layer depends on liquid crystal molecules contained therein and is approximately in a range of 1.4-1.6. The emission angle of the light substantially remains unchanged after passing through the base substrate 326 and the liquid crystal layer 33. One reason for the leakage light is that a distorted electric field is generated between the pixel electrode on the color filter substrate and the pixel electrode and date line on the array substrate such that liquid crystal molecules are aligned irregularly, causing an abnormal display. Most of the light leaking out may be blocked by the black matrix 311 arranged on the color filter substrate 31. However, there is a problem when the liquid crystal display is impacted by an external force, the panel 30 may become concave downwardly, as shown in FIG. 4. In this case, the black matrix 311 provided in place for blocking light may shift with respect to the array substrate by a distance of d2 and an shift region is formed, as shown in FIG. 5. Thus, light passing through the gap between the light-blocking strip 324 and the data line 323 may further leak out through the shift region. Then, a phenomenon called touch mura occurs. The touch mura is more obvious when more light leaks out through the shift region.
A method has been proposed to prevent the leakage light and touch mura by increasing the area of the black matrix disposed on the color filter substrate such that even when the black matrix shifts by a distance, light passing through the gap between light-blocking strip and the data line can be till blocked. The method, however, brings about another problem, that is, increasing the area of the black matrix reduces the area of transmissive region, giving rise to a reduced aperture ratio and a degraded display quality.